In precision instrument making there is often the need to provide rotatable drive rolls with which elements arranged in the interior of a housing can be adjusted. In such cases, the drive roll is intended to be actuated from outside and is fixed so as to limit displacement in the axial direction. Applications of such drive rolls include, for example, adjustment rings on objective lenses and focusing drives on binoculars.
For reasons of space and cost, sliding bearings are normally used for the radial and axial mounting of the drive rolls. In this case, it is known that for sliding bearings to be free-running it is necessary that they exhibit some bearing play, both in the radial and in the axial directions. In contrast, sliding bearings set without play are not free-running and have temperature-dependent and load-dependent torque differences and, as a result, their ability to be adjusted is considerably restricted.
DE 35 40 322 A1 discloses a rolling contact bearing which comprises two concentric bearer rings having approximately V-shaped grooves in the mutually facing outer surfaces. Likewise, V-shaped steel inlays can be inserted into the grooves, and serve as running surfaces for the rolling elements. The rolling elements can be, in particular, rolls arranged crosswise, or balls which can be held by a cage. The opening angle of the groove in the bearer ring can be slightly smaller than that of the inlay. During the assembly of the rolling contact bearing, the inlays are then forced into the corresponding grooves in the bearer rings, over the rolling elements, by means of slight resilient deformation. In this way, a spring-prestressed rolling contact bearing is produced as an installed element which is intended to be particularly advantageous for spasmodic, high-vibration and fast-moving operation.
Parallel to the outer surfaces bearing the grooves, the rolling contact bearing has a central hole to accommodate the axis of rotation of a component to be carried by the rolling contact bearing. The spring prestress of the rolling bodies within the rolling contact bearing is oriented radially with respect to the central hole. Elimination of play of the mounting of the component on the axis of rotation can be achieved only by means of appropriately fitting the holder of the rolling contact bearing in the component and the axis of rotation in the hole in the rolling contact bearing. The rolling contact bearing itself has no influence either on the mounting of the component in the axial direction on the axis of rotation.
DE 1 929 815 U discloses a rolling contact bearing having bearing rings of large diameter which are located on the outside and inside an axis of rotation and offset from one another in the axial direction. Special pressure means, which act on the shoulder of either the outer or inner bearing ring, produce via the rolling elements a permanent prestress with respect to the shoulder of the respective other bearing ring. As a result, the rolling contact bearing is self-adjusting without play in the axial direction and is suitable to accommodate high axial and radial loads and tilting moments. The rolling contact bearing is not adjustable in the radial direction with respect to the axis of rotation.
For the installation of conventional ball bearings, the wall thicknesses available on the housing and in the drive roll are frequently inadequate. In addition, in fine instrument making there is often inadequate space available for the installation of special prestressing means for setting bearing play.